A new microemulsion method using tetraoctylammonium bromide as a cationic surfactant has beenformulated to fabricate thiol-functionalized gold nanoparticles. The nanoparticles were compared withthose synthesized by the multistep Brust two-phase method. The nanoparticle sizes and size distributionsfabricated by the two methods were characterized by UV–vis absorbance spectroscopy and transmittanceelectron microscopy. The simple microemulsion method produced the same results as those obtained bythe Brust method.